Microwave operated mechanism



Feb. 3, 1948.

l/OLTA GE VOL TA 65 VOLTAGE R. s. CL-APP 2,435,423

MICROWAVE OPERATED MECHANISMS Filed March 22, 1944 W TIME TIME Patenied Feb. 3, 1948 MICROWAVE OPERATED MECHANISM Richard G. Clapp, Haverford, Pa anignor, by nieene assignments, to Philoo Corporation,

Philadelphia, Pa, a corporation of Pennsyl- Application March 22, 1944, Serial No. 527,618

Claims.

This invention relates to wireless power transmission systems, and more particularly to a novel method and apparatus for operating mechanisms through the agency of high frequency wave energy. By the present invention there is provided a, novel arrangement for utilizing directed wave energy to operate mechanisms, such as the small electric motors employed in clocks or timers.

The principal object of the invention is to provide a novel method and means for effecting the transmission and reception of wave energy to operate electrical mechanisms, without the use of wires for such transmission.

It is a further object of the invention to provide a. synchronous clock or control mechanism which can be driven by radio frequency power over short distances without the need of intervening wire connections.

Another object of the invention is to provide a power transmission and utilization system, which is capable of providing efficient operation with transmitting equipment of the type presently available.

Other objects and features of the invention will be apparent as the description proceeds.

The invention itself will best be understood by reference to the following drawings, in which:

Fig. 1 is a, schematic diagram of a-preferred.

form of the invention; and

Figs. 2, 3, and 4 are graphical illustrations used in explaining the operation of the circuit of Fig. 1.

Referring to Fig. 1, pulses of ultra high frequency carrier wave energy (interrupted continuous waves) are generated by the source hearing the reference character I. As is well understood by those skilled in the art, these pulses of wave energy'may be radiated in substantial accordance with the laws of geometrical optics. This may be accomplished through the agency of a directional radiating system comprising, for example, the di-.

pole 2 and the parabolic reflector 3. These pulses of transmitted energy may then be received by a conventional, preferably directional, receiving antenna which may comprise, for example, the parabolic reflector 4, and a folded dipole 5.

At the receiving end there is provided a suitable rectifying means 6-which is conveniently a crystal detector-for rectifying the interrupted continuous waves received from the source I. The rectifier load circuit comprises the field winding 1 of a motor which includes, in addition to the said field winding, a rotor or armature 8. The field winding 1 is tuned, by means of a shunt condenser 9, to the pulse frequency of the source pulse frequency is 60 cycles per second, or some multiple or submultiple thereof, it is usually preferred to fix, or determine, the pulse frequency by tying in the pulse forming circuits of the source with the power line frequency, either directly or through the agency of frequency multipliers or the like, as is well understood in the art.

In general the motor elements 1 and 8 may be constructed in accordance with conventional small-motor practice. Where the motor I, 8 is intended for use in driving a, clock mechanism or timing device, the arrangement should be such as to maintain the desired synchronism between the input or pulse frequency and the rotation of the rotor 8.

In order to obtain reasonable emciency of transmission of radio frequency energy (even for so small a load as a clock) a very narrow beam must be transmitted. To secure very narrow beams economically requires the use of ultra high transmission frequencies, since only through the use of very high frequencies can the parts of the directional antenna system be small. While the present invention is not limited to any particular range of carrier frequencies, it is preferred, in the interests of antenna economy. to employ frequencies of the order of ten-thousand megacycles or higher. This is equivalent to a wave length of three centimeters or less.

Most of the high frequency wave generators presently available have low efliciencies in (or are unsuited to) continuous operation. For example, the magnetron is eminently suited for generating carrier waves having frequencies of the order suitable for use with the present invention, but these devices are not suited for continuous operation. However, the efliciency of the magnetron oscillator is very acceptable when employed as a generator of high amplitude interrupted continuous waves, especially where the interval between the individual wave groups is large compared to the duration of the group. Accordingly, it is an important feature of the present invention to employ a high frequency wave generator whose output is of the type generally known as an interrupted continuous wave, and to so modify the motor circuit as to enable it to operate efliciently in response to relatively short, widely spaced pulses of electrical energy. Since interrupted continuous wave generators are well known in the art, and since the structure thereof forms no part of the present invention, it is deemed unnecessary to describe the wave source in detail, except to say that the duration of each pulse may be, for

I, e. g. 60 cycles per second. Where the desired exampl of the order of a millisecond or a microinto oscillation at the pulse frequency.

3 second, i. e., short compared to the time interval between pulses, which in a 80 cycle system is about 17 milliseconds.

Since alternating current electric motors are conventionally constructed and arranged to operate from a source of voltage having a substantially sine wave form, it will be evident that such motors are'not well adapted to operate directly from the rectified pulse output of the detector 8. Assume that the interrupted continuous wave output of the transmitter I is represented by the wave representation of Fig. 2, in which each of the wave trains it! has a duration which is short compared to the interval between the trains. By way of example, the wave trains in may occur at the rate of sixty per second. Upon rectification there results, in the output of the detector 8. a pulse voltage similar to that illustrated in Fig. 3. This sixty cycle pulse voltage is applied to the terminals of the resonant circuit I, 9,.

which is shock excited by the rectified pulses ii Since the impedance of the tuning condenser 9 is negligible at the high carrier frequencies employed, the only voltage occurring across the resonant circuit will be a somewhat distorted sixty cycle sine wave. This voltage is illustrated at I! in Fig. 4. The effect of the pulses ii in distorting this wave is here evident.

Preferably the pulse frequency of the exciting pulses is substantially equal to the resonant frequency of said-circuit. Alternatively, however, the pulse frequency may be a submultiple of said resonant frequency. Thus, for example, a synchronous clock motor resonant at 60 cycles might be driven at a predetermined speed with signals having pulse frequencies of either 60 or 30 cycles, or, in general, with signals having a pulse frequency equal to one-nth the resonant frequency, where n is a. small integer.

electrical power into mechanical power, said lastnamed means comprising elements including a the-form of interrupted continuous waves. means Referring again to the receiving portion of the system, the crystal rectifier 8 should be chosen to give high efiiciency at fairly high signal levels, rather than minimum noise at low signal levels as is done in some high frequency practices.

Where carrier waves of the order of one to three centimeters are employed, appropriate transmitting and receiving antennas may be con- I able support'on one of the floors above. In the base of the clock there may be provided a down- ,wardly directed receiving antenna 4. 5 whose output terminals are connected to a suitable rectifier as shown in Fig. 1.

While the present invention has been described with particular reference to the single illustrated embodiment, it will be understood that the invention is susceptible of substantial modification within the limits defined by the following claims.

I claim:

1. A wireless system for operating an'electrical mechanism by means of power transmitted at hyper frequencies, comprising means for generating pulses of carrier wave energy substantially in the form of interrupted continuous waves.

means for radiating said wave energy, means for receiving said wave energy. means responsive to said received wave energy for establishing a for radiating said wave energy, means for receiving. said wave enerslh means responsive to said received wave energy for establishing a low frequency pulse signal, a synchronous motor, said motor including a field winding tuned to the nth harmonic of the pulse frequency, where nmay be any small integer, and connections for impressing said low frequency pulse signal on said tuned field winding, said tuned winding being shock excited into continuous oscillation by said pulse signal.

3. In a system for converting an electrical pulse signal into mechanical power, a source of periodictime-spaced pulse signals, the duration of each pulse being small compared to the time interval between pulses, means for converting electrical power into mechanical power, said' means comprising elements including a winding tuned to the nth harmonic of the pulse frequency; where n is a small integer, and connections for impressing said pulse signals on said tuned winding, said tuned winding being shock excited into continuous oscillation by said pulse signals.

4. In a system for converting an electrical pulse signal into mechanical power, a source of periodic time-spaced pulse signals, the time duration of each pulse being small compared to the time interval between pulses, a synchronous motor, said motor including a winding tuned to the nth harmonic of the pulse frequency, where 1: may be any small integer, and connections for impressing said pulse signals on said tuned winding, said tuned winding being shockexcited into continuous'oscillations by said pulse signals.

5. In a system for converting an electric pulse signal into mechanical power, a source of periodic time-spaced pulse signals, the duration of each pulse being small compared to the time 'interval between pulses, an electric motor including a winding tuned to the nth harmonic of the pulse frequency, where n is a small integer, and connections for impressing said pulse signals on said tuned winding, said tuned winding being shock excited into continuous oscillations by said Pulse si nals.

6. Apparatus for operating an electric motor u pulses having the same rate of occurrence, and a tuned winding forming part of said motor con- ,nected to said last-named means for shock excitation by said pulses.

'7. Apparatus for operating an electric motor -by means of time-spaced high frequency wave trains radiated from a remote point and having a relatively low rate of occurrence, comprising means for receiving said wave trains, means for converting said wave trains into time-spaced low frequency pulse-signal, means for converting 7 pulses having the same rate of occurrence, and

an oscillatory circuit including a field winding of said motor connected to said last-named means for shock excitation by said pulses.

8. A system for operating a low frequency electric motor by means of high-frequency wave energy, comprising means for producing timespaced pulses of said wave energy having a low rate of occurrence, means for rectifying said pulses of high frequency wave energy to produce pulses at a frequency corresponding to said rate, an electric motor including a winding, said motor being operable by a low frequency alternating voltage, an oscillatory circuit including said winding adapted to produce an operating voltage for said motor in response to said lastnamed pulses, and means for supplying said lastnamed pulses to said oscillatory circuit.

9. A system for operating a low frequency electric motor by means of high frequency wave energy, comprising means for producing timespaced pulses of said wave energy having a low rate of occurrence, means for rectifying said pulses of high frequency wave energy to produce pulses at a frequency corresponding to said rate, an electric motor including a winding, said motor being operable by a low frequency alternating voltage, a condenser connected in shunt with said winding and forming therewith a resonant circuit adapted to produce an operating voltage for said motor in response to said lastnamed pulses, and means for applying said lastnamed pulses across the terminals of said resonant circuit.

- I 10. A method of operating a motor at low irequency by means or high frequency wave energy.

which comprises producing time-spaced pulses of said wave energy having a low rate of occurrence, rectifying said pulses of high frequency wave energy to produce pulses .at a frequency corresponding to said rate, and utilizing said lastnamed pulses to produce a low frequency alternating voltage capable of operating said motor.

RICHARD G. CLAPP,

BEI'ERENCES CITED The following references are of record in the tile 01' this patent:

UNITED STATES PATENTS OTHER REFERENCES "Tube Control of A.-C. Motors by J. Ryder in the publication Electronics for April 1936. 

